Gas turbines recover a proportion of the kinetic energy of the gases being expelled from the combustion chamber to operate the fan, compressor and accessories in a turboreactor, or alternatively to drive the transmission shaft of the propeller, the compressor and various accessories in a turboprop engine.
FIG. 1 represents a longitudinal section of a gas turbine 1.
Gas turbine 1 shown in FIG. 1, with longitudinal axis XX′, has four stages: each stage contains a distributor 2A, 2B, 2C and 2D, followed by a rotor 3A, 3B, 3C and 3D.
More specifically, each distributor 2A, 2B, 2C and 2D is formed by an annular row of stator blades 2. At their tips, stator blades 2 of distributor 2A, 2B, 2C and 2D have an external platform 21 and 21′, and at their roots an internal platform 22 and 22′. It should be noted that external platforms 21 and 21′ are joined end-to-end circumferentially around longitudinal axis XX′. In the same way, internal platforms 22 and 22′ are also joined end-to-end circumferentially around longitudinal axis XX′. In addition, each rotor 3A, 3B, 3C and 3D is formed by an annular row of rotor blades.
Distributors 2A, 2B, 2C and 2D are installed between an outside casing 4 and an internal structure 5, while rotors 3A, 3B, 3C and 3D are attached to discs 6A, 6B, 6C and 6D, which are bolted to one another.
Turbine 1 also contains rings 7A, 7B, 7C and 7D, assembled concentrically around rotors 3A, 3B, 3C and 3D of each stage to contain the flow of gases traversing the various stages in airstream 8 of turbine 1. Each ring 7A, 7B, 7C and 7D consists of ring sectors 7, 7′, which hold in position distributors 2A, 2B, 2C and 2D and form a sealing means with the tips of the rotor blades of rotors 3A, 3B, 3C and 3D.
To improve the sealing in airstream 8 of turbine 1 it is known to fit sealing plates 10, which can be seen in FIGS. 2 to 4b, between two successive ring sectors 7, 7′, between two adjacent external platforms 21 and 21′ and between two adjacent internal platforms 22 and 22′ of two successive stator blades. The addition of sealing plates 10 prevents gas leaks between two adjacent platforms and between two adjacent ring sectors, which may reduce the turbomachine's performance.
When sealing plate 10 is used to seal space Ec between two adjacent external platforms 21, 21′ it is fitted in a first aperture 13 made in a first side face 11 of a first external platform 21 and in a second aperture 14 made in a second side face 12 of a second external platform 21′. It should be noted that first side face 11 of first external platform 21 and second side face 12 of second external platform 21′ are adjacent, and apertures 13 and 14 are facing one another. In addition, when sealing plate 10 is used to seal space Ec between two adjacent internal platforms 22, 22′ sealing plate 10 is fitted in a first aperture 13 made in a first side face 11 of a first internal platform 22 and in a second aperture 14 made in a second side face 12 of a second internal platform 22′. In the same way, to seal space Ec between two adjacent ring sectors 7, 7′, sealing plate 10 is fitted in a first aperture 13 made in a first side face 11 of a first ring sector 7 and in a second aperture 14 made in a second side face 12 of a second ring sector 7′. It should be noted that first side face 11 of first ring sector 7 and second side face 12 of second ring sector 7′ are adjacent, and apertures 13 and 14 are facing one another
However, such sealing plates 10 become worn or become disengaged from apertures 13 and 14. Indeed, the combined vibratory phenomena at high temperatures in airstream 8 when the turbomachine is in operation causes wearing of sealing plates 10, which move and vibrate at the bottoms of apertures 13 and 14 by the force of the gases, leading to premature wear. Depending on the locations of the leaks, an increase of gas leaks through space Ec can cause reduced cooling of the parts of turbine 1, which may cause more or less significant burns, and result in impaired performance.